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feat(llamaswap): add llama-swap provider + canonical imagegen interface
Add provider/llamaswap, a tailored provider for llama-swap (the model-swapping
proxy over llama.cpp / stable-diffusion.cpp). Its chat path delegates to
provider/openai at {base}/v1 — no duplicated wire client (ADR-0007) — with
legacy max_tokens, a Bearer no-key placeholder for keyless local instances, and
a timeout-free client so cold model swaps rely on context deadlines. The
"tailored" surface is concrete management methods (ListModels / Running /
Unload) that don't belong on the canonical llm.Provider interface. The
llama-swap:// DSN scheme builds an http base URL (local-first); a no-URL
built-in errors clearly on use, mirroring foreman.

Add imagegen, a new canonical text-to-image interface separate from llm
(Request/Result/Model/Provider; Image = llm.ImagePart so generated images feed
straight back into chat). First backend is llama-swap via OpenAI
/v1/images/generations (b64_json, bytes-only). Re-exported from the root. v1 is
txt2img only.

Hermetic httptest coverage for chat delegation, management endpoints, image
decode, and scheme wiring. ADR-0015 + ADR-0016, README support matrix +
image-gen section, CLAUDE.md package map, and progress.md updated in the same
commit.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-27 15:01:54 -04:00

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# ADR-0015: llama-swap provider
**Status:** Accepted — 2026-06-27
## Context
llama-swap (https://github.com/mostlygeek/llama-swap) is an on-demand
model-swapping proxy in front of llama.cpp (and stable-diffusion.cpp) servers:
it extracts the `model` from each request, loads/hot-swaps the matching
upstream, and serves it. It is what foreman reached for, but more robust
(groups, TTL unload, health checks, a management API). We want it as a
first-class majordomo target — `llama-swap://token@host:port` in the DSN — and
the user explicitly asked for a *tailored* provider, not a bare alias of the
OpenAI client.
The tension: llama-swap's **chat** API is byte-for-byte OpenAI Chat
Completions. A new hand-rolled chat wire client would duplicate
`provider/openai` for zero behavioral gain, which ADR-0007 forbids. But the
"more robust" surface (model discovery, running list, unload) does not fit the
canonical `llm.Provider`/`llm.Model` interface (anti-creep: no provider-specific
features leak into the canonical API).
## Decision
- A dedicated `provider/llamaswap` package, but its chat path **delegates to
`provider/openai`** pointed at `{baseURL}/v1` — no duplicated wire client.
`Provider.Model` returns `openai.New(...).Model(id)`.
- Chat construction specifics: `WithLegacyMaxTokens()` (llama.cpp's OpenAI shim
honors `max_tokens`, not `max_completion_tokens`); a placeholder `Bearer
no-key` when no token is set (the openai client treats a blank key as a
synthetic 401, but a local keyless llama-swap ignores a bearer it didn't ask
for); the injected HTTP client carries **no timeout** — a cold model swap
blocks up to llama-swap's `healthCheckTimeout` (≥15s), so callers bound work
with a context deadline, never a client timeout.
- The "tailored" surface lives as **concrete methods** on `*llamaswap.Provider`,
outside the canonical interface: `ListModels` (GET `/v1/models`), `Running`
(GET `/running`, returned as raw JSON — its shape is not a stable contract),
`Unload` (POST `/api/models/unload[/:model]`). A small `doJSON` helper shares
bearer auth + error mapping; non-2xx → `*llm.APIError` (so `llm.Classify`
applies), transport errors wrapped raw.
- DSN: the `llama-swap` scheme builds an **http://** base URL from the host
(llama-swap is local-first), deliberately *not* the DSN's https-always
`BaseURL()`. A TLS-fronted instance can use the `openai://` scheme for chat.
A no-DSN built-in `llama-swap` provider registers but errors on use (mirrors
foreman).
- Image generation is implemented here too, against the new `imagegen`
interface (see ADR-0016).
## Consequences
- No new dependency, no duplicated chat client; the chat path inherits every
openai feature/fix automatically.
- Management methods are reachable only by holding the concrete
`*llamaswap.Provider` (e.g. mort), not through `Parse`/`llm.Provider` — the
correct boundary for non-canonical features.
- `Running`'s raw-JSON return is honest about llama-swap not publishing a stable
schema; a typed shape can be added later without breaking callers that ignore
it.